Process for removing dust from light sensitive photographic emulsions



Jan. 12, 1943. E. HELLMIG ETAL. 2,303,005

PROCESS FOR REMOVING DUST FROM LIGHT SENSITIVE PHOTOGRAPHIC EMULSIONS Filed Jan. 9, 1940 Ehrhobrd Hellmg Hans Kocmmer&

IN VENTORS THE IR ATTORNEYS Patented Jan. 12, 1943 PROCESS FOR REMOVING DUST FROM LIGHT SENSITIVE PHOTOGRAPHIC EMUL- SIONS Ehrhard Hellmig and Hans Kammerl, Dessau, Germany, asslgnors to General Aniline & Film Corporation, New York Delaware N. Y., a corporation of Application January 9, 1940, Serial No. 313,092

In Germany January 2, 1939 9 Claims.

This invention relates to dust-retaining layers of photographic materials. The surface of packing material which comes in contactwith light sensitive photographic layers was mainly selected from the view point not to cause any chemical damage or mechanical harm, for instance by scratching. For this reason the back of the protecting paper adjacent to the next following outer winding of the light sensitive layer was manufactured as smooth as possible.

As far as precautions for the protection of the light sensitive layer are concerned, it has been entirely overlooked that, in spite of strict control of the light sensitive material to avoid carefully dust as much as possible, it still may be damaged by dust particles. They adhere to the surface being in contact with the layer, for instance, the

surface of rollfllm-protectlng-paper and wrapping paper, or the dust forms on them. It is a known fact that dust on the photographic layer aflects greatly the quality of the image, this is especially true for enlargements irom dust-damaged negatives.

It was found, however, that by a suitable preparation of the paper surface, prior to its use for acids, for instance glycerol and phthalic acid or diglycollic acid and 1-3 butylene-glycol, also polymeric hydrocarbons, for instance polyisobutylene photographic materials, detrimental dust-effects may be completely suppressed. According to this invention the surfaces therefore are coated with dust-retaining layers, or dust-retaining substances are added to the material being in direct contact with the photographic layer. With rollillms rolled up without protecting paper, for instance motion picture fllms, the detrimental dusteii'ects may be completely overcome by applying a dust-retaining coating to the back of the emulsion base.

Such coatings, impregnations and admixtures are mostly applied in form of solutions. Pure solutions of special dust-retaining characteristics may be used, of which after evaporation or the,

solvent the dust-retaining compound is left over, or mixed solutions may be applied in such a way, that special dust-retaining compounds are added to the usual surface coating, so that after "evaporation of the solvent a lacquer coating of the desired eil'ect containing the dust-retaining compound remains.

Most useful as dust-retaining compounds are viscous materials, for instance polymerisation products on the styrol basis, condensation resins, polymerisates of the vinyl group, for instance polyvinylacetate, polyvinylether. Very suitable are also solid synthetic resins which, when dry, retain a certain stickiness, for instance condensation products of polyhydric alcohols and polybasic and cellulose esters of higher fatty acids, for instance cellulose trilaurate. Suitable high viscous materials or synthetic resins of that type are available under the registered trade names of Movilith NNN, Albanol, Alkydal BG, Oppanol, Lutonal, Cellorit.

The dust-retaining compounds are added to I the protecting layers, applied mostly in the form of lacquer coatings, in such a quantity that the treated surface has a far greater dust-absorbing power than the light sensitive emulsion. According to the viscosity of the dust-retaining compounds and the requirements for the protecting layers a quantity of few percent is mostly suillcient.

In the accompanying drawing some embodiments of the invention are shown in a simplified manner, not representing the actual proportions of the cross-sections.

Figure 1, sectional view, shows a rolliilm with protecting paper having a dust-retaining layer on its back.

Figure 2, a film rolled up without protecting paper, having therefore a dust-retaining layer on the back of the emulsion base.

Figure 3, sectional view represents, part of a cut film having a paper sheet between each film.

Figure 4, sectional view, two light sensitive cut films in close contact, one on top of theother.

Figure 5, sectional view, a sheet of packing pa per for light sensitive photographic material.

A rollfllm (Fig. 1) consisting of alight sensitive emulsion layer I and a. support 2 is fastened in a known manner by an adhesive tape 3 to a protecting paper I, with which the him is rolled onto the rollillm spool I. In the rolling-up-operation the outer film layer with the emulsion side 1 comes continuously in contact with the back of y the protecting paper 4. In order to avoid that dust from the protecting paper adheres to the light sensitive emulsion layer, the paper is coated with a dust-retaining backing, which for instance may be obtained by means of the following solution:

Polyvinylether grams 2 Benzene do retaining layer 6, which is obtained by applying the following solution:

Polyvinylether grams 3 Celluloid do '7 Ether do 30 ered with a sheet of paper 1, which at least on the side facing the emulsion, preferably on both sides, is coated with a dust-retaining layer according to Example 1 or 2.

Figure 4 represents two light sensitive materials, for instance'cut films or photographic pa pers, contacting each other without protecting paper in between. They consist of a support 2 and a light sensitive emulsion layer I. In order to avoid that dust from the back of the film or paper-sheet reaches the light sensitive layer, the back of the support is coated with a dust-retaining layer according to Example 1 or 2.

Figure 5 shows in sectional view a sheet of packing paper 8 for light sensitive photographic material, which carries on one side a dust-retaining layer 6. In many cases it will be advantageous to coat the packing paper for light sensitive material on both sides with a dust-retaining layer.

Contrary to the usual preparations of the back of a rollfilm-protecting-paper, the surfaces prepared according to the present invention are not smooth anymore, but of a more or less rough character. Contrary to the opinion prevailing till noW it was found that no damage occurs to the light sensitive layer by a rough surface, whereas the light Sensitive emulsion layers turned out to be completely dust-free afterwards, even when previously dusted on purpose. Such negatives with no damaging dust particles'may be enlarged in an excellent way.

We claim:

1. A process for removing dust from light sensitive photographic materials which comprises applying a dust-retaining layer to materials coming loosely in contact with the light sensitive emulsion layer and causing said dust-retaining layer to come into contact with said emulsion layer prior to its use said dust-retaining compound having a higher dust retaining power and adhesiveness than said emulsion layer.

3. A light sensitive photographic material in which a dust-retaining layer is provided loosely in contact with the light sensitive layer said dustretaining layer having a higher dust retaining power and adhesiveness than said emulsion layer.

4. A photographic rollfilm which comprises a light sensitive silver halide emulsion layer, a support (2) for said emulsion layer (I), a protecting paper (4), said protecting paper having a dustretaining layer (6) on the side and part which is loosely in contact with the photographic emulsion layer, said layer (6) possessing a higher dust-retaining power and adhesiveness than said emulsion layer. I

5. A cinematographic. rollfilm which comprises a light sensitivesilver halide emulsion layer (I),

a support (2) for said emulsion layer, said support having a dust-retaining layer on its back adjacent to the photographic emulsion layer, said layer possessing a higher dust-retaining power and adhesiveness than said emulsion layer.

6. A package of light sensitive photographic material in which the protecting wrapping paper is coated on the side adjacent to the photographic emulsion layer with a dust-retaining layer, said layer possessing a higher dust-retaining power and adhesiveness than the light sensitive emulsion layer of said photographic material.

7. A process for removing dust from light-sensitive photographic materials which comprises bringing the surface of the light-sensitive emulsion layer into contact with adust-retaining layer prior to use of said emulsion layer, said dustretaining layer having a higher dust-retaining power and adhesiveness than said emulsion layer.

8. A process for removing dust from photographic rollfilm comprising a light-sensitive film and protective paper, which process comprises applying a dust-retaining layer to the side and part of the paper which is in contact with the emulsion layer of the light-sensitive film when it is rolled and rolling said rollfilm to bring about contact between said emulsion layer and said dust-retaining layer, said dust-retaining layer having a higher dust-retaining power and adhesiveness than said emulsion layer.

9. A process for removing dust from motion picture film comprising a light-sensitive emulsion layer and a support therefor, which process comprises applying a dust-retaining layer to the back of the support and winding said film to bring about contact between said emulsion layer and said dust-retaining layer, said dust-retaining layer having a higher dust-retaining power and adhesiveness than said emulsion layer.

EHRHARD HELLMIG. HANS KAMMERL. 

